Sandra has 4 math tests this marking period. She recieved 90%, 87%, and 92% on the first 3. with is the minimal score she needs on her last test in order to average at least 90% in math class?
Let the unknown score be x (Sum of the scores)/(number of tests) = avg (90+87+92+x)/4 = 90 (269+x)/4 = 90 269 + x = 90*4 269 + x = 360 x = 360-269 = 91
So Sandra needs a minimal score of 91% on her last test in order to average at least 90% in math class
